1. Field of the Invention
The invention relates to the technical field of the herbicides and plant growth regulators, preferably the herbicides for controlling unwanted vegetation or the herbicides for the selective control of broad-leaved weeds and weed grasses in crops of useful plants, or the plant growth regulators which can be used for influencing the growth of crop plants.
2. Description of Related Art
In their application, crop protection agents known to date for the selective control of harmful plants in crops of useful plants or active compounds for controlling unwanted vegetation sometimes have disadvantages, be it (a) that they have no or else insufficient herbicidal activity against particular harmful plants, (b) that the spectrum of harmful plants which can be controlled with an active compound is not wide enough, (c) that their selectivity in crops of useful plants is too low and/or (d) that they have a toxicologically unfavourable profile. Furthermore, some active compounds which can be used as plant growth regulators for a number of useful plants cause unwanted reduced harvest yields in other useful plants or are not compatible with the crop plant, or only within a narrow application rate range. Some of the known active compounds cannot be produced economically on an industrial scale owing to precursors and reagents which are difficult to obtain, or they have only insufficient chemical stabilities. In the case of other active compounds, the activity is too highly dependent on environmental conditions, such as weather and soil conditions.
The published patent applications EP-A-5341, EP-A-266725, EP-A-270830, JP-04/297454, JP-04/297455, JP-05/058979, WO 2011/003775, WO 2011/003776, WO 2011/042378, WO 2011/073143 and WO 2011/098417 disclose herbicidal cyanobutyrates.
EP-A-5341 describes herbicidal esters and amides of 4-cyano-3,4-diarylbutanoic acids. The aryl radicals mentioned are optionally substituted phenyl radicals and unsubstituted pyridyl or thienyl. The specific examples include mainly 4-cyano-3,4-diphenylbutanoic acids and esters. There are two specific examples of compounds containing pyridyl, namely 4-cyano-3-phenyl-4-(pyridin-3-yl)butanoic acid and the corresponding ethyl ester.
According to EP-A-5341, the threo isomers are generally suitable for the non-selective control of harmful plants, whereas the erythro/threo isomer mixtures are suitable for the selective control of harmful plants in some crops of useful plants. Moreover, EP-A-5341 mentions that the 2 enantiomers belonging to the threo form differ in their activities, which was studied in an exemplary manner using the different activities of the enantiomers of the enantiomer pair of 4-cyano-3,4-diphenylbutanoic acid having unsubstituted phenyl radicals.
EP-A-266725 discloses a number of erythro/threo isomer mixtures of 4-cyano-3,4-diphenylbutanoic acids and derivatives thereof which can be used selectively for the control of weeds in rice crops.
EP-A-270830 describes that threo isomers and erythro/threo isomer mixtures of 4-cyano-3,4-diarylbutanoic acid (esters) can be used as plant regulators, preventing the development of an infructescence in various harmful grasses. The aryl radicals mentioned are optionally substituted phenyl radicals and unsubstituted pyridyl or halogen-substituted pyridyl. Specific examples relate mainly to (substituted) 4-cyano-3,4-diphenylbutanoic acid (esters). Additionally described are also 4-cyano-3-pyridyl-4-phenylbutanoic acid esters, such as the compound ethyl 4-cyano-3-pyridyl-4-phenylbutanoate, or 4-cyano-3-phenyl-4-pyridylbutanoic acid ester, such as the compound methyl 4-cyano-3-(4-chlorophenyl)-4-(6-fluoropyridin-3-yl)butanoate. JP-04/297455 discloses herbicidal 4-cyano-3-phenyl-4-heteroarylbutanoic acid (esters), where the heterocyclic radicals are selected from the group consisting of 1,2,4-triazolyl, 1-pyrazolyl, 1-imidazolyl, 2- and 3-thienyl, 2- and 3-pyridyl, 1-methylpyrrol-2-yl, 2-quinolinyl, 2-methyl-3-trifluoromethylpyrazol-5-yl and 5-trifluoromethylpyridin-2-yl. Specific compounds from the 3-pyridyl series only comprise unsubstituted pyridin-3-yl radicals, for example the compounds propargyl and allyl 4-cyano-3-phenyl-4-(pyridin-3-yl)butanoate.
WO 2011/003775 discloses specific esters of 4-cyano-3,4-diphenylbutanoic acids which can be used as effective herbicides, preferably also in crops of useful plants. WO 2011/003776, WO 2011/042378, WO 2011/073143 and WO2011/098417 disclose 4-cyano-3,4-diphenylbutanoic acids and esters which have specific substitutions at the phenyl radicals and can be used as effective herbicides, preferably also in crops of useful plants.
The herbicidal activity of the known compounds of the class of substances mentioned, in particular at low application rates, and/or their compatibility with crop plants remain deserving of improvement.
For the reasons mentioned, there is still a need for alternative, highly active herbicides for the selective application in plant crops or use on non-crop land. It is also desirable to provide alternative chemical active compounds which may be used in an advantageous manner as herbicides or plant growth regulators.
Likewise desirable are compounds having herbicidal activity which are highly effective against economically important harmful plants even at relatively low application rates and can be used selectively in crop plants, preferably with good activity against harmful plants.